This invention relates to a bearing assembly for use in environs in which particular attention must be given to cleanliness and/or where resistance to oxidation is paramount, such as in the food or chemical industry. More specifically, this invention relates to a bearing assembly having a cast iron housing coated in part with a low friction, chemically resistant polymer coating.
In the food, chemical and environmental industries there is a great need for a bearing assembly which resists rust, and will not chip, flake or deteriorate in severe wet operating environments or under high pressure washdowns. It is also important, in such environments, that the housing not be subject to corrosion from chemicals normally encountered during use. In the past, cast iron housings of such bearing assemblies have been nickel plated to render the housing resistant to the chemical and environmental demands. In one example, where a ball bearing insert is to swivel into a spherical bore of a ball bearing housing, the housing bore dimensions are controlled to give a specified swivel torque. This procedure is used for a standard line of ball bearings.
When nickel plating is applied to such a ball bearing housing, the spherical bore must be machined oversize to allow for the plating buildup, and requires an additional set up over standard machining operations. Furthermore, due to variations in plating thickness, ball bearing inserts to be used with the plated housings must be graded by size and a trial and error assembly procedure has to be employed to achieve a desired swivel torque with the assembly.
Various and sundry products have heretofore been coated with fluorocarbon polymers such as a polytetrafluorotheylene, or products themselves have been made of such products, particularly to take advantage of low friction characteristics of the polymer. It is also believed, though not known, that bearing inserts may have been produced before and coated with fluorocarbon polymers.
Bearing assemblies according to the present invention represent improvement over the prior art. Particularly, bearing assemblies according to the present invention are fully protected from the environment, are more uniform, and operate at desired assembly torque levels. Moreover, with assemblies according to the present invention, trial and error matching of housings and inserts is no longer necessary.